车辆间通信信道的仿真模型分析

主要对车辆间通信的环境进行分析。对3种经典的车辆间通信信道模型,即级联Nakagami信道、级联瑞利信道和双选择衰落信道(时间选择性和频率选择性)进行详细论述,并对这3种信道模型下BPSK调制的误码率性能进行仿真,并对仿真结果进行分析。     

Capacity of the mismatched Gaussian channel

Information capacity is determined for the additive Gaussian channel when the constraint is given in terms of a covariance different from that of the channel noise. These results, combined with previous results on capacity when the constraint covariance is the same as the noise covariance, provide a complete and general solution for the information capacity of the Gaussian channel without feedback. The results are valid for both continuous-time and discrete-time channels and require only two assumptions: the noise is due to a stochastic process with sample paths having finite energy over the observation period (w.p.1), and the constraint is given in terms of a Hilbert space norm. Such a constraint is implicit in any constraint giving finite capacity.     

Power control with coder-estimator sequences

Power control is an important issue in mobile communication systems and has been studied extensively in the literature. This paper has taken on a new perspective and modeled the problem as a state estimation problem with finite communication constraints. The problem is solved by using the 1-bit mean coder-estimator sequence. The performance of the coder-estimator sequence is compared with that of the simple feedback power control technique by evaluating their respective fade margins as in commonly done in radio system engineering.     

混合D2D蜂窝网络中基于模拟退火算法的资源调度策略

D2D通信是未来5G网络中一种近距离直通通信方式,在通信过程中,信息直接由发送端传给接收用户,而不需要经过基站的转发.在传统蜂窝网络中引入D2D通信可以极大地提升系统的总吞吐量、增大频谱资源的利用率以及降低发射终端的功耗.主要介绍了一种适用于混合D2D蜂窝网络中的资源分配方法,通过拉格朗日乘子法结合模拟退火算法实现频谱资源的分配,提出一种同时考虑信道容量和能耗的基于模拟退火算法的资源调度策略.本算法在维也纳仿真平台上经仿真验证,相比于传统贪婪优化算法,可以明显增大系统总吞吐量和频谱资源利用率.另外,算法中采用了分布式资源调度方法,D2D用户根据算法步骤自行搜索适合的目标信道并计算其发射功率,可以有效减少基站的信令开销.     

基于CC1101的车间无线通信系统设计

针对无线通信技术在车间通信方面的不断发展,提出了一种车间无线数据交换系统并对其动静态性能做出研究,为其能够在车辆碰撞预警中应用做好前期的理论和试验研究。该系统是以单片机STC12C5a60S2为微处理器,基于无线收发芯片CC1101的通信模块系统。对其工作原理和工作方式进行了分析,给出了其软硬件设计,阐述了通信模块的接口实现过程,并在硬件测试中验证了所设计的系统在静态及低速动态环境中性能良好。     

Self-Configuring TDMA Protocols for Enhancing Vehicle Safety With DSRC Based Vehicle-to-Vehicle Communications

This paper presents a novel Medium Access Control protocol for inter-vehicular wireless networking using the emerging Dedicated Short Range Communication (DSRC) standards. The main contribution of the paper is the design of a self- configuring TDMA protocol capable of inter-vehicle message delivery with short and deterministic delay bounds. The proposed Vehicular Self-Organizing MAC (VeSOMAC) is designed to be vehicle location and movement aware so that the MAC slots in a vehicle platoon can be time ordered based on the vehicles' relative locations for minimizing the multi-hop delivery delay. A novel feature of VeSOMAC is its in-band control mechanism for exchanging TDMA slot information during distributed MAC scheduling. It is shown that by avoiding explicit timing information exchange, VeSOMAC can work without inter-vehicle time synchronization. The in-band control mechanism is also used for fast protocol convergence during initial network setup and topology changes due to vehicle movements. A simulation model has been developed for comparing VeSOMAC's performance with that of DSRC-recommended 802.11 MAC protocol for highway traffic safety applications.     

Longitudinal control of a platoon of vehicles with no communicationof lead vehicle information: a system level study

The paper considers the problem of longitudinal control of a platoon of automotive vehicles on a straight lane of a highway and proposes control laws in the event of loss of communication between the lead vehicle and the other vehicles in the platoon. After discussing the main design objectives for the proposed control laws, the authors formulate these objectives as a constrained optimization problem. By solving this optimization problem, they obtain longitudinal control laws for a platoon of vehicles which does not use any communication from the lead vehicle to the other vehicles in the platoon. Comparison between these control laws and the control laws which use such a communication link to transmit lead-vehicle information to the other vehicles in a platoon shows that, in the case of loss of communication between the lead vehicle and the other vehicles, the performance of the longitudinal control laws degrades; however, this degradation is not catastrophic     

智能反射面辅助MU-MISO系统宽带信道估计算法

为适应移动通信系统的宽带化应用,针对智能反射面（Intelligent Reflecting Surface,IRS）辅助多用户多输入单输出系统信道估计问题,提出了一种基于稀疏矩阵分解的改进正交匹配追踪（Orthogonal Matching Pursuit,OMP）算法。首先,考虑基站导频约束及IRS相移约束,建立一个压缩感知模型。然后,通过自适应地细化变换矩阵的分辨率,避免稀疏信号的细节丢失;再利用信道在不同子载波处共享的公共稀疏性,对多个子频带进行联合估计。最后利用级联信道的双结构稀疏性,将信道估计扩展至多用户场景。仿真结果表明,与传统压缩感知算法相比,所提算法能以较小的导频开销获得更高的准确性。     

Linear Unbiased State Estimation with Random One-Step Sensor Delay

Sensor delay and observation uncertainty often occur in modern computer-based systems, e.g., when the measurement is transmitted to a remote controller through a network medium. In this paper, we revisit the Kalman filter design problem for a stochastic dynamic system with random one-step sensor delay, and derive the optimal unbiased state estimation algorithm. Both full- and reduced-order filters are studied, and the results compare favorably with those of the existing algorithms in examples via simulation.     

Smart antennas in wireless systems: uplink multiuser blind channeland sequence detection

Space-division multiple-access (SDMA) schemes have been proposed to increase the capacity of wireless communication systems by simultaneously transmitting and receiving multiple co-channel signals through different spatial channels. We address the uplink (remote users to the base station antenna array) blind channel and sequence identification problem for an SDMA system. We show that multiuser blind identification can be accomplished by exploiting the spatial and temporal diversities of an antenna array system. In particular, a recursive estimation algorithm is developed to recover multiple signals from intersymbol interference (ISI) and co-channel interference (CCI) by taking advantage of a special structure of the array output and the finite-alphabet property of digital communication signals. The implementation of the proposed approach in practical applications is discussed, and field experiments have been conducted to demonstrate the effectiveness of the proposed algorithm     

一种超宽带模拟合并转发协作通信系统

针对频率选择性衰弱信道下协作通信系统信道估计复杂的问题,提出了一种模拟合并放大转发超宽带(UWB)协作通信方案.该方案在源节点处对发送符号进行实数分布式空时编码并附加传输参考,在中继节点处利用传输参考对多径分量进行模拟合并,从而构建了一种改进型非正交放大转发协作通信系统.仿真结果证明,相对于无协作通信系统,模拟合并转发...     

基于正交解扩的信干比估计方法

研究了TDD-CDMA(时分双工-码分多址)系统中的SIR(信干比)估计问题。现有的SIR估计方法准确度依赖于信道条件和观测时间,而TDD-CDMA系统复用时隙短,车速条件下信道变化剧烈的特点使得估计准确度降低。针对这种情况,提出了一种基于正交解扩的SIR估计方法。通过COSSAP仿真对比结果表明,该方法在瑞利衰落信道和AWGN(加性高斯白噪声)信道条件不同调制方式下,从低SIR到高SIR的很大范围内都有比较好的性能。     

Gamma-Gamma大气湍流中部分相干光通信系统性能研究

部分相干光在湍流大气中传输时,可以有效抑制湍流所引起的光强闪烁效应,从而改善通信链路性能。针对Gamma-Gamma大气湍流信道模型和部分相干光的光束特性,得到了采用OOK调制方式下部分相干光通信系统的平均误码率、中断概率和平均信道容量三个性能指标的解析表达式;在此基础上,分析了光束的空间相干长度和通信距离对通信链路的性能影响。计算结果表明,在相同的大气湍流条件和传输距离下,随着部分相干光的空间相干长度的减小,系统的误码率和中断概率逐步降低,在平均信噪比为30 dB时,系统的误码率可以达到10-5,中断概率低于10-6;另外,系统的平均信道容量会随着光束相干长度的减小而增加,在信噪比等于12 dB时,平均信道容量达到3.8 b/sHz-1。分析结果为部分相干光在湍流大气中实现可靠通信提供了理论依据。     

Information capacity of the stationary Gaussian channel

The averaged information capacity of the mismatched stationary continuous-time Gaussian channel is considered, in the limit as the observation time becomes infinite. It is required only that the signal satisfy a reproducing kernel Hilbert space constraint on expected energy. This requires the, signal energy to be distributed in regions where the noise energy, is not too small, and is the weakest condition that provides finite capacity. In the case when both the noise covariance and the filter on the message are expressed by rational functions, the results complement those previously obtained by Gallager and Holsinger (1968), and the combination gives a complete solution to the capacity problem. The treatment provides a desirable generality on the class of transmitted signals that is not present in previous treatments     

Connected vehicle driving safety enhancement via dynamic communication channel selection

Vehicle-to-Vehicle communication can cogently improve traffic safety because it grants drivers better situational awareness and strengthens inter-cooperation among them. However, the current policy obliges the safety-critical messages, i.e., Basic Safety Messages (BSMs) and Event Safety Messages (ESMs), to be transmitted exclusively in one single channel over the Dedicated Short-Range Communication (DSRC) spectrum, which may incur severe channel congestions, intolerable communication delays, and higher accident probabilities. To alleviate the channel congestion, popular measures focus on adaptively adjusting the transmission parameters, e.g., packet generating rate. However, due to the narrow bandwidth of a single channel, these methods can hardly ensure timely delivery of critical safety-related messages when the density of DSRC-enabled vehicles becomes high. Instead of sticking to only one single channel, this paper applies a dynamic channel selection algorithm to thoroughly exploit the entire DSRC band resource and reduce the transmission delay. To demonstrate the effectiveness of the utilized algorithm, we conduct experiments under two representative scenarios, i.e., a cooperative adaptive cruise control scenario and a run-the-red-light scenario at an intersection. Experimental results show that the transmission delays of both the BSMs and the ESMs could be effectively reduced, yielding an improved vehicle platoon control accuracy, string stability, and collision avoidance performance.     

An information theoretic foundation of synchronized detection

The constrained capacity of a coherent coded modulation (CM) digital communication system with data-aided channel estimation and a discrete, equiprobable symbol alphabet is derived under the assumption that the system operates on a flat fading channel and uses an interleaver to combat the bursty nature of the channel. It is shown that linear minimum mean square error channel estimation directly follows from the derivation and links average mutual information to the channel dynamics. Based on the assumption that known training symbols are transmitted, the achievable rate of the system is optimized with respect to the amount of training information needed. Furthermore, the results are compared to the additive white Gaussian noise channel, and the case when ideal channel state information is available at the receiver     

基于多中继导频频分复用的协同通信系统信道估计算法

本文针对频率选择性衰落环境下结合正交频分复用技术的放大转发多中继协同通信系统,提出了基于导频频分复用的频域信道估计算法,包括最小二乘（LS）估计算法和线性最小均方误差（LMMSE）估计算法。理论分析和仿真结果表明,该算法不仅成功分辨了多中继协同通信系统的所有频域信道衰落系数,避免了各中继节点转发的导频符号在目的节点上的混叠干扰,而且减少了频域信道估计所需的导频符号数量和时隙周期长度,提高了协同通信系统的传输效率和频谱利用率,同时显著提高了信道估计的精度,降低了算法的复杂度,具有较高的实用价值。      

A novel feedback scheme to increase throughput in multiple access radio systems

To enhance the throughput of a slotted ALOHA control channel in a radio communication system, we present and analyze a method for estimating the number of remote stations that are attempting to transmit to a central base station. Each of the contending remote stations randomly chooses to transmit with probability p. Our novel contribution is the use of information concerning the number of successful packet transmissions that arrive without retransmission (i.e., that are successfully received on their first transmission attempt), as a metric for accurately and robustly estimating the number of contending remote stations. This estimate is determined at the base station and then used to compute the optimal transmission probability p that is used as feedback to the remote stations for their use. The proposed estimation method is analyzed and shown to provide good steady‐state performance for a variety of system models, including situations with noise and idling remote stations. The scheme is also shown to provide good tracking capabilities. This revised version was published online in August 2006 with corrections to the Cover Date.     

Semiblind maximum-likelihood demodulation for CDMA systems

This correspondence addresses the problem of channel estimation and symbol detection in wireless direct-sequence code-division multiple-access (DS-CDMA) communication systems. We introduce a novel multiuser demodulation scheme that proceeds in two steps. First, the multiaccess channel parameters are estimated according to a suitable modification of the maximum-likelihood (ML) criterion using the expectation maximization (EM) algorithm. Subsequently, this estimate and other useful side information are employed to perform ML detection of the transmitted symbols with the Viterbi algorithm. Our main contribution is the development of a novel stochastic ML method for channel estimation that takes advantage of all the available statistical information referred to the transmitted signals and channel noise. Additionally, it can incorporate the knowledge of a fraction of the transmitted symbols; hence, the term semiblind. Computer simulation results are presented that show how close-to-optimum performance is achieved in time-dispersive fading channels using remarkably short training sequences     

Hierarchical Longitudinal Controller for Rear-End Collision Avoidance

Rear-end collision is a very serious problem in modern traffic situations, and there have been a great number of research reports on the longitudinal control method for road vehicles. In many cases, however, the control problem is formulated under platoon configuration and for some predictable noncollision situations. For predictable collision situations, regional and hierarchical approaches have been employed, but these approaches render difficulties due to ignorance for modeling error and logical error in a decision process. In this paper, the vehicle control for collision avoidance is studied with two control objectives, i.e., minimization of the safety distance error and regulation of the relative velocity between two vehicles. For this, a longitudinal controller using terminal sliding mode (TSM) with hierarchical structure is proposed for rear-end collision avoidance. The TSM is employed to achieve convergence in finite time, while the hierarchical approach is used for the system to accommodate the intelligence of the driver to handle various situations. The effectiveness of the proposed control scheme is verified by software simulations